Drivers

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Table of Contents#

Driver Concept
PushDriver Abstract Class
OneSignalDriver — Mobile (iOS/Android)
OneSignalWebDriver — Web
Conditional Imports via onesignal_factory.dart
Creating a Custom Driver

Driver Concept#

A push driver wraps a platform-specific push SDK. The PushChannel delegates all SDK calls to whichever driver is registered with NotificationManager.setPushDriver(). Drivers expose a uniform API regardless of the underlying SDK (OneSignal, FCM, etc.), so channel logic never depends on SDK internals.

PushDriver Abstract Class#

dart

abstract class PushDriver {
  String get name;
  bool get isSupported;
  Future<PushPermissionState> permissionState();
  bool get isOptedIn;

  Future<void> initialize(Map<String, dynamic> config);
  Future<void> login(String externalId);
  Future<void> logout();
  Future<String?> currentExternalId();
  Future<String?> currentSubscriptionId();
  Future<bool> requestPermission();
  Future<void> optIn();
  Future<void> optOut();
  Future<void> setTags(Map<String, String> tags);
  Future<void> removeTag(String key);

  Stream<PushNotificationEvent> get onNotificationReceived;
  Stream<PushNotificationEvent> get onNotificationClicked;
  Stream<PushPermissionState> get onPermissionChanged;
  Stream<PushIdentityChange> get onIdentityChanged;

  Future<PushReachability> reachability(); // implemented in the base class
}

Key Members#

Member	Description
`name`	Driver identifier string (e.g., `'onesignal'`)
`isSupported`	Synchronous platform check; `PushChannel.isAvailable` delegates here
`permissionState()`	Reads the current `PushPermissionState`. Asynchronous on both platforms: mobile reads the native permission over a platform channel, web reads the browser's own `Notification.permission`.
`isOptedIn`	Whether the user is actively subscribed to push
`initialize(config)`	One-time SDK init; must be called before all other methods
`login(externalId)`	Associates a user account with the push subscription
`logout()`	Removes the external user ID from the subscription
`currentExternalId()`	Reads back the external id the device is currently subscribed as, or `null` when not initialized or unset. Closes the loop on `login`/`logout`: without it nothing can tell whether the SDK acted on the identity it was given.
`currentSubscriptionId()`	Reads back the platform subscription id, or `null` when not initialized or unsubscribed. A push cannot be addressed without one, which is why `reachability()` consults it.
`requestPermission()`	Triggers the OS permission dialog; returns `true` if granted
`optIn()` / `optOut()`	Re-subscribe / unsubscribe without clearing the external ID
`setTags(tags)`	Segmentation tags for OneSignal targeting
`onNotificationReceived`	Broadcast stream; fires when a notification arrives while the app is in foreground
`onNotificationClicked`	Broadcast stream; fires when the user taps a notification
`onPermissionChanged`	Broadcast stream; fires on OS permission state transitions
`onIdentityChanged`	Broadcast stream of `PushIdentityChange` events; fires whenever the SDK itself reports the user or subscription changed underneath the app. The only trustworthy confirmation that a `login`/`logout` actually landed.
`reachability()`	Whether push can actually reach this device right now (see below). Implemented once in the base class; drivers do not override it.

PushNotificationEvent#

dart

class PushNotificationEvent {
  final Map<String, dynamic> data;
  const PushNotificationEvent(this.data);
}

The data map contains the notification's additionalData payload (mobile) or the JS event data (web).

PushIdentityChange#

dart

class PushIdentityChange {
  final String? externalId;
  final String? subscriptionId;
  final bool? optedIn;
  const PushIdentityChange({this.externalId, this.subscriptionId, this.optedIn});
}

Every field is nullable because a single SDK event reports only part of the state: a user change carries the external id, a subscription change carries the subscription id and the opt-in flag. A null field means "this event did not report it", never "it is empty".

Reachability#

PushDriver.reachability() derives a four-state answer instead of each driver declaring one, so every driver answers the same way:

State	Meaning
`PushReachability.unavailable`	No platform driver here at all (`isSupported == false`).
`PushReachability.blocked`	Permission was denied and the platform will not re-prompt. The app has to point the person at the OS/browser setting; calling `requestPermission()` again silently no-ops.
`PushReachability.off`	Never asked, or asked and not opted in. Safe to call `requestPermission()`.
`PushReachability.on`	Permitted, opted in, and holding a subscription id — the only state a push can actually reach.

dart

final reachability = await driver.reachability();

This is the read a soft-prompt UI should gate on before showing itself, and the read that answers "can I send this device a push" without ever raising the OS dialog.

OneSignalDriver — Mobile (iOS/Android)#

OneSignalDriver wraps the onesignal_flutter package.

dart

class OneSignalDriver extends PushDriver {
  @override
  String get name => 'onesignal';

  @override
  bool get isSupported => Platform.isIOS || Platform.isAndroid;

  @override
  Future<PushPermissionState> permissionState() async {
    if (!_initialized) return PushPermissionState.notDetermined;

    final native = await OneSignal.Notifications.permissionNative();
    return switch (native) {
      OSNotificationPermission.authorized => PushPermissionState.authorized,
      OSNotificationPermission.provisional ||
      OSNotificationPermission.ephemeral =>
        PushPermissionState.provisional,
      OSNotificationPermission.notDetermined =>
        PushPermissionState.notDetermined,
      // Only iOS reports a real tri-state; elsewhere permissionNative
      // collapses onto denied, so ask the SDK whether a prompt would still
      // show. It does only when the device has never been asked.
      OSNotificationPermission.denied =>
        await OneSignal.Notifications.canRequest()
            ? PushPermissionState.notDetermined
            : PushPermissionState.denied,
    };
  }

  @override
  Future<String?> currentExternalId() async =>
      _initialized ? OneSignal.User.getExternalId() : null;

  @override
  Future<String?> currentSubscriptionId() async =>
      _initialized ? OneSignal.User.pushSubscription.id : null;

  @override
  Future<void> initialize(Map<String, dynamic> config) async {
    final appId = config['app_id'] as String?;
    OneSignal.initialize(appId!);

    OneSignal.Notifications.addForegroundWillDisplayListener((event) {
      _receivedController.add(
        PushNotificationEvent(event.notification.additionalData ?? {}),
      );
    });

    OneSignal.Notifications.addClickListener((event) {
      _clickedController.add(
        PushNotificationEvent(event.notification.additionalData ?? {}),
      );
    });

    // The observer carries a bare bool; re-read permissionState() instead of
    // collapsing the tri-state onto denied.
    OneSignal.Notifications.addPermissionObserver((permission) {
      unawaited(permissionState().then(_permissionController.add));
    });

    OneSignal.User.addObserver((state) {
      _identityController.add(
        PushIdentityChange(externalId: state.current.externalId),
      );
    });

    OneSignal.User.pushSubscription.addObserver((state) {
      _identityController.add(
        PushIdentityChange(
          subscriptionId: state.current.id,
          optedIn: state.current.optedIn,
        ),
      );
    });

    _initialized = true;
  }

  @override
  Future<void> login(String externalId) => OneSignal.login(externalId);

  @override
  Future<void> logout() => OneSignal.logout();

  @override
  Future<bool> requestPermission() =>
      OneSignal.Notifications.requestPermission(true);

  @override
  Future<void> optIn() => OneSignal.User.pushSubscription.optIn();

  @override
  Future<void> optOut() => OneSignal.User.pushSubscription.optOut();

  @override
  Future<void> setTags(Map<String, String> tags) =>
      OneSignal.User.addTags(tags);

  @override
  Stream<PushIdentityChange> get onIdentityChanged =>
      _identityController.stream;
}

Listening to Events#

dart

final driver = NotificationManager().pushDriver as OneSignalDriver;

driver.onNotificationReceived.listen((event) {
  final title = event.data['title'];
  // show in-app snackbar
});

driver.onNotificationClicked.listen((event) {
  final url = event.data['action_url'];
  MagicRoute.to(url);
});

OneSignalWebDriver — Web#

OneSignalWebDriver communicates with the OneSignal Web SDK v16 via JavaScript interop through OneSignalJsInterop.

dart

class OneSignalWebDriver extends PushDriver {
  @override
  String get name => 'onesignal';

  @override
  bool get isSupported => kIsWeb;

  @override
  Future<void> initialize(Map<String, dynamic> config) async {
    await OneSignalJsInterop.init(
      appId: config['app_id'],
      safariWebId: config['safari_web_id'],
      notifyButtonEnabled: config['notify_button_enabled'] ?? false,
    );
  }

  @override
  Future<void> login(String externalId) => OneSignalJsInterop.login(externalId);

  @override
  Future<bool> requestPermission() => OneSignalJsInterop.requestPermission();
}

The web driver also exposes additional getters that surface JS interop values:

dart

final webDriver = NotificationManager().pushDriver as OneSignalWebDriver;

print(webDriver.subscriptionId);  // OneSignal subscription UUID
print(webDriver.externalId);      // currently logged-in external user ID
print(webDriver.oneSignalId);     // OneSignal internal user ID

Conditional Imports via onesignal_factory.dart#

The service provider never imports OneSignalDriver or OneSignalWebDriver directly. It calls createOneSignalDriver() from onesignal_factory.dart, which uses Dart's conditional import system:

dart

// onesignal_factory.dart
import 'onesignal_stub.dart' if (dart.library.html) 'onesignal_web.dart';

PushDriver createOneSignalDriver() => createPlatformDriver();

On web: dart.library.html is available → onesignal_web.dart is imported → returns OneSignalWebDriver()
On mobile: the stub is imported → returns OneSignalDriver()

This means the entire onesignal_flutter dependency (which uses dart:io) is tree-shaken out of the web build, and the JS interop code is tree-shaken out of the mobile build.

Creating a Custom Driver#

To add FCM or another push service, extend PushDriver:

dart

import 'package:magic_notifications/magic_notifications.dart';

class FcmDriver extends PushDriver {
  final StreamController<PushNotificationEvent> _receivedController =
      StreamController<PushNotificationEvent>.broadcast();
  final StreamController<PushNotificationEvent> _clickedController =
      StreamController<PushNotificationEvent>.broadcast();
  final StreamController<PushPermissionState> _permissionController =
      StreamController<PushPermissionState>.broadcast();
  final StreamController<PushIdentityChange> _identityController =
      StreamController<PushIdentityChange>.broadcast();

  @override
  String get name => 'fcm';

  @override
  bool get isSupported => !kIsWeb && (Platform.isIOS || Platform.isAndroid);

  @override
  Future<PushPermissionState> permissionState() async =>
      PushPermissionState.notDetermined;

  @override
  bool get isOptedIn => false;

  @override
  Future<void> initialize(Map<String, dynamic> config) async {
    // FirebaseMessaging.instance.getToken(); etc.
  }

  @override
  Future<void> login(String externalId) async { /* store token */ }

  @override
  Future<void> logout() async { /* remove token */ }

  @override
  Future<String?> currentExternalId() async => null;

  @override
  Future<String?> currentSubscriptionId() async => null;

  @override
  Future<bool> requestPermission() async {
    // NotificationSettings settings = await FirebaseMessaging.instance.requestPermission();
    return false;
  }

  @override
  Future<void> optIn() async {}

  @override
  Future<void> optOut() async {}

  @override
  Future<void> setTags(Map<String, String> tags) async {}

  @override
  Future<void> removeTag(String key) async {}

  @override
  Stream<PushNotificationEvent> get onNotificationReceived =>
      _receivedController.stream;

  @override
  Stream<PushNotificationEvent> get onNotificationClicked =>
      _clickedController.stream;

  @override
  Stream<PushPermissionState> get onPermissionChanged =>
      _permissionController.stream;

  @override
  Stream<PushIdentityChange> get onIdentityChanged =>
      _identityController.stream;

  // reachability() is inherited from the base class; no override needed.
}

Register it with the manager's driver registry in your service provider's boot() (see Notification Manager for the resolution order):

dart

@override
Future<void> boot() async {
  final manager = NotificationManager();
  manager.extend('fcm', () => FcmDriver());
  await manager.pushDriver.initialize(
    {'project_id': Config.get('notifications.push.project_id')},
  );
}

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